Vane-type camshaft phasers for varying the timing of combustion valves in an internal combustion engines are well known. In a vane-type phaser, timing advance and retard chambers are formed within the phaser between inwardly-extending lobes of a generally cylindrical stator and outwardly-extending vanes of a rotor concentrically disposed within the stator. Typically, a camshaft phaser is disposed on the front of an engine and includes an oil control valve for controlling oil flow into and out of the chambers. The valve receives pressurized oil from an oil gallery in the engine block and selectively distributes oil to controllably vary the phase relationship between the engine's camshaft and crankshaft.
A known problem with prior art vane-type phasers is leakage of oil past the vanes between the advance and retard chambers. Such leakage can result in slow and imprecise response of a phaser. In prior art phasers, the inner and outer radial interfaces between the rotor vanes and the stator walls are sealed by resilient wipers disposed in either the vanes or the stator. However, the axial interfaces between the rotor vanes and the phaser front cover plate surface on one side, and between the rotor vanes and the rear cover plate surface on the other side, depend solely upon tight clearances for sealing. Specifically, tight tolerances for length, parallelism, and flatness are required on the mating surfaces to minimize leakage across the vanes; however, to permit rotation of the rotor within the stator, the axial height of the rotor vanes must be slightly less than the axial height of the stator, so that some leakage across this length gap is inherent. Over time, the height difference may increase with wear, resulting in a corresponding increase in leakage and decrease in phaser performance.
What is needed in the art is means for positive sealing of the gap at the axial faces of rotor vanes in a vane-type camshaft phaser.
It is a principal object of the present invention to prevent hydraulic leakage between the advance and retard chambers in a vane-type camshaft phaser.